An asteroid or comet similar to the one that wiped out the dinosaurs smacked into Earth 251 million years ago, triggering the biggest extinction in Earth history. The findings by scientists from the University of Washington, University of Rochester, NASA, and New York University are published in the Feb. 23 issue of Science and provide the strongest evidence yet that an impact played a role in the extinction known as "the Great Dying."
The impact of the asteroid or comet, estimated to be anywhere from six to 12 kilometers wide, would have released unimaginable fury. "The impact of a bolide of this size releases an amount of energy that is basically about 1 million times the largest earthquake recorded during the last century. It was like a magnitude 12.0 earthquake on the Richter scale," says Robert Poreda, associate professor of earth and environmental sciences at the University of Rochester and one of the authors.
The impact and rapid extinction occurred simultaneously with some of the most extensive volcanic activity the world has ever seen: More than 1.6 million cubic kilometers of lava, enough to cover the entire planet with 10 feet of lava had it spread evenly around the globe, oozed out of the ground in Siberia in a relatively short amount of time, less than 1 million years.
"It was the proverbial blast from the double-barreled shotgun," Poreda says. "We're not sure of all the environmental consequences, but with both the impact and with the volcanic activity, we do know that Earth was not a happy place. It may be that the combined effects of impact and volcanism are necessary to cause such a tremendous extinction."
The evidence for the impact comes in the form of cosmic stowaways, helium and argon molecules formed elsewhere in the universe that survived a journey through space and crashed into Earth as part of the impact. The molecules were encased in carbon molecules known as buckyballs, which are big enough to hem i
Contact: Tom Rickey
University of Rochester